Intermediate Thermal Equilibrium Observed in Quantum System

In a great many ways, it seems Nature always prefer states of equilibrium. This is why air tries to fill a vacuum, electric currents flow, and an object's temperature tries to approach that of its surroundings, at least at the macroscale. At the quantum scale, things can be quite different from what we would expect, and researchers at the Vienna University of Technology have discovered this as they observed atoms reaching a pre-thermalized state.

The researchers started with a one dimensional Bose-Einstein condensate, which means all of the atoms within the gas behaved as though they were one particle. This was then cut in two and the separate pieces were held next to each other. Because these two lines of atoms had different energies for a time, they produced an interference pattern with their matter waves, and by observing the interference pattern, the researchers can monitor as the atoms approach equilibrium. What they found though was that the atoms do not go directly to equilibrium but actually stop at an intermediate state and remain there for some time. Importantly, this intermediate step still has information about the condensate from when it was split in two, which is normally lost when equilibrium is achieved.

This finding has many implications from particle physics to quantum computers. Particles within a quantum computer want to reach equilibrium, just like any other particle, but if they do, the information they held is lost, so the existence of this relatively long-lived intermediate step could prove very useful.